Laws of Molecular Force. 3 



The difference for each CH 2 group is *97 from C 2 H 6 to C 6 H 14 , 

 •90 from C 6 H 14 to C 8 H 18 , and '85 from C 8 H 18 to Ci H 22 . 

 There appears to be a progressive diminution in these differ- 

 ences for CH 2 . It will be of advantage, therefore, to study 

 a more extended series, such as is given on page 266 of the 

 " Laws of Molecular Force " for the paraffins from C 5 H 12 

 to C 16 H 34 , the values of M 2 Z being got, as there explained, 

 from Bartoli and Stracciati's surface-tensions at 11° C. To 

 complete the series we can obtain approximate values of M. 2 l 

 for C 3 H 8 and C 4 H 10 by the approximate relation MZ = 1 190 v t T b , 

 given on page 247 of the " Laws of Molecular Force," dividing 

 by 10 6 to reduce to the same units as are employed in 

 table xxv. T b is the boiling-point measured from absolute 

 zero, and v x is the volume of a gramme at the boiling-point : 

 for C 3 H 8 , T A = 246 and ^ = 1-75 ; and for C 4 H 10 , T b = 2U and 

 v 1 = l , 71 ; and thus the values of M 2 / to go along with the rest 

 are 22*1 and 32*3 ; and for (M 2 /)* we have the series of values 

 and differences : — 



Table I. 



C 2 H 6 . C 3 H 8 . C 4 H ]0 . C 5 H 12 . C 6 H U . C 7 H lff . C 8 H 18 C 9 H 20 . 



(M 2 /)* 3-8 | 47 | 57 | 6-9 | 7 6 | 8-8 | 9*5 | 10-5 



Diff. -9 10 1-2 -7 1-2 -7 10 



C 10 H 22 . C U H 24 . C 12 H 26 . C 13 H 28 . O 14 H 30 . C 15 H 32 . C, 6 H 34 . 



(MH)i | 11-3 | 12-1 | 13-1 | 13-8 | 14-7 | 15*2 | 10 



Diff. -8 -8 1-0 7 "9 -5 -8 



Here, although the values of the differences for CH 2 are 

 unsteady (doubtless on account of the difficulty of preparing 

 the paraffins pure), there is on the whole a progressive dimi- 

 nution in the value of the difference : thus from C 2 H 6 to C 8 H 18 

 the difference is 5' 7, and from C 8 H 18 to C 14 H 30 it is 5*2 But 

 in the case of the esters from C 3 H 6 2 to C 10 H 20 O 2 , to which 

 we proceed, there is no such diminution. The following are 

 the mean values of (M 2 /)^ for the different isomers under each 

 formula : — 



Table II. 



C 3 H 6 2 . C 4 H 8 2 . C 5 H 10 O 2 . C 6 H 12 2 . C 7 H 14 2 . C 8 H 16 2 . 



(M.H)? 5-8 | 6-7 | 7-6 | 8-4 | 9-3 | 102 



Diff. -9 -9 -8 -9 -9 



C9H 18 2 . C 10 H 20 O 2 . 



(M 2 Z)* | 11-3 | 12-1 



Diff. 1-1 -8 



The mean difference is here *9, which is the mean difference 



B 2 



